Selectively called radio receiver with bit rate detection for battery at shorter than a frame period

Abstract

In a selectively called radio receiver operable in a battery saving method in which frame synchronism is established after establishment of bit synchronism and in which a bit rate detection signal is produced by detecting a bit rate of an arriving radio signal to establish the frame synchronism before lapse of a frame synchronism establishing interval after establishment of the bit synchronism or restoration of bit synchronism subjected to a failure, repeated production of the bit rate detection signal at a regular interval is monitored by determining for the regular interval a unit time interval shorter than a frame period of the radio signal. Preferably, the unit time interval is equal to a four-codeword length of codewords, such as the frame period, when sixteen is the number of codewords in a typical frame.

What is claimed is: 
     
       1. A battery saving method for use in a selectively called radio receiver comprising a receiver section put in an intermittently activated state while waiting for reception of a radio signal, having a signal bit rate and comprising successive frame periods, as a reception signal to establish bit synchronism between said receiver section and said reception signal, and wherein said receiver section is put in a temporary continually activated state to establish frame synchronism with frame periods of said reception signal following establishment of said bit synchronism, said battery saving method comprising the steps of: detecting, with said receiver section put in a repeatedly activated state for a bit rate detection period spaced by a bit rate detection interval when an error occurs in bit synchronism, the bit rate of said reception signal as a detected bit rate in said bit rate detection period;   producing a bit rate detection signal upon coincidence of said detected bit rate with said signal bit rate; and   switching said receiver section into a temporary continuously activated state to establish said frame synchronism before lapse of a frame synchronism establishing interval following activation of said receiver section to said repeated activated state, wherein said switching step comprises the steps of:   determining a unit time interval shorter than each of said frame periods; and   using said unit time interval repeatedly as said bit rate detection interval.   
     
     
       2. A battery saving method as claimed in claim 1, wherein said determining step begins to determine, during said frame synchronism establishing interval, said unit time interval immediately following first production of said bit rate detection signal. 
     
     
       3. A battery saving method as claimed in claim 2, wherein said using step repeatedly checks production of said bit rate detection signal once within said unit time interval during said frame synchronism establishing interval. 
     
     
       4. A battery saving method as claimed in claim 1, wherein said using step comprises the steps of: checking, during said frame synchronism establishing interval immediately following first production of said bit rate detections signal, repeated production of said bit rate detection signal; and   switching said receiver section into said repeatedly activated state if check of said repeated production fails.   
     
     
       5. A battery saving method as claimed in claim 4, said radio signal comprises frame periods of a predetermined number of codewords of a common codeword length, wherein said determining step determines said unit time interval is not longer than a fraction of a total length of the codewords in each of said frame periods. 
     
     
       6. A battery saving method as claimed in claim 5, wherein said predetermined number is equal to an integral multiple of four, and wherein said determining step determines said unit time interval corresponds to four times said common codeword length. 
     
     
       7. A battery saving method as claimed in claim 1, said radio signal comprises frame periods of a predetermined number of codewords of a common codeword length, wherein said determining step determines said unit time interval is not longer than a fraction of a total codeword length of the codewords in each of said frame periods. 
     
     
       8. A battery saving method as claimed in claim 7, wherein said predetermined number is equal to an integral multiple of four, and wherein said determining step determines said unit time interval corresponds to four times said common codeword length. 
     
     
       9. A selectively called radio receiver, operable in a battery saving mode, for receiving a radio signal having a bit rate and comprising successive frame periods, said radio receiver comprising: a receiver section put in an intermittently activated state while waiting for reception of said radio signal as a reception signal to establish bit synchronism between said receiver section and the bit rate of said reception signal, and wherein said receiver section is put in a temporary continually activated state to establish frame synchronism with frame periods of said reception signal following establishment of said bit synchronism;   bit rate detecting means for detecting, when said receiver section is put in a repeatedly activated state of being activated for a bit rate detection period spaced by a bit rate detection interval when an error occurs in bit synchronism, the bit rate of said reception signal as a detected bit rate in said bit rate detection period to produce a bit rate detection signal upon coincidence of said detected bit rate with said signal bit rate; and   control means for switching said section to a temporary continuously activated state to establish said frame synchronism before lapse of a frame synchronism establishing interval immediately following activation of said receiver section into said repeatedly activated state, wherein aid control means comprises:   determining means for determining a unit time interval shorter than each of said frame periods; and   using means for using said unit time interval repeatedly as said bit rate detection interval.   
     
     
       10. A selectively called radio receiver as claimed in claim 9, wherein said determining means begins to determine, during said frame synchronism establishing interval, said unit time interval immediately following first production of said bit rate detection signal. 
     
     
       11. A selectively called radio receiver as claimed in claim 10, wherein said using means repeatedly checks for production of said bit rate detection signal once within said unit time interval during said frame synchronism establishing interval. 
     
     
       12. A selectively called radio receiver as claimed in claim 9, wherein said using means comprises: checking means for checking, during said frame synchronism establishing interval immediately following first production of said bit rate detection signal, repeated production of said bit rate detection signal; and   switch back means for switching back said receiver section into said repeatedly activated state if check of said repeated production fails.   
     
     
       13. A selectively called radio receiver as claimed in claim 12, said radio signal comprises frame periods of a predetermined number of codewords of a common codeword length, wherein said determining means determines said unit time interval is not longer than a fraction of a total codeword length of the codewords in each of said frame periods. 
     
     
       14. A selectively called radio receiver as claimed in claim 13, wherein said predetermined number is equal to an integral multiple of four, and wherein said determining means determines said unit time interval corresponds to four times said common codeword length. 
     
     
       15. A selectively called radio receiver as claim in claim 12, said radio signal comprises frame periods of a predetermined number of codewords of a common codeword length, said control means comprising switching means for switching said receiver section to said temporary continuously activated state following production of said bit rate detection signal during said frame synchronism establishing interval; and a word counter for counting, upon production of said bit rate detection signal, a word count of said codewords towards a prescribed number which is not less than said predetermined number, said word counter producing a word count signal representative of said word count, wherein:   said checking means comprises:   timer means responsive to said word count signal for producing a pulse signal each time when said unit time interval lapses during progress of said frame synchronism establishing interval;   holding means for holding said bit rate detection signal as a held detection signal until reset by said pulse signal and for producing said held detection signal as a holding means output signal; and   gating means responsive to said pulse signal for gating said holding means output signal as a gating means output signal;   said switch back means detecting, during said frame synchronism establishing interval, whether or not said gating means output signal is repeatedly present, said switch back means switching and keeping said receiver section to said repeatedly activated state when said gating means output signal is not present and to said temporary continuously activated state when said gating means output signal is present.   
     
     
       16. A selectively called radio receiver as claimed in claim 15, wherein: said word counter begins to count said word count upon first production of said bit rate detection signal;   said timer means first produces said pulse signal when said word counter begins to count said word count.   
     
     
       17. A selectively called radio receiver as claimed in claim 15, wherein said determining means determines said unit time interval is not longer than a fraction of a total codeword length of the codewords in each of said frame periods. 
     
     
       18. A selectively called radio receiver as claimed in claim 17, wherein said predetermined number is equal to an integral multiple of four, and wherein said determining means determines said unit time interval corresponds to four times said common codeword length. 
     
     
       19. A selectively called radio receiver as claimed in claim 9, said radio signal comprising frame periods a predetermined number of codewords of a common codeword length, wherein said determining means determines said unit time interval is not longer than a fraction of a total codeword length of the codewords in each of said frame periods. 
     
     
       20. A selectively called radio receiver as claimed in claim 19, wherein said predetermined number is equal to an integral multiple of four, and wherein said determining means determines said unit time interval corresponds to four times said common codeword length. 
     
     
       21. A battery saving method for use in a selectively called radio receiver comprising a receiver section for receiving a radio signal, having a signal bit rate and comprising successive frame periods, as a reception signal to establish bit synchronism between said receiver section and said reception signal, and wherein said receiver section establishes frame synchronism with frame periods of said reception signal following establishment of said bit synchronism, said battery saving method comprising the steps of: detecting the bit rate of said reception signal for a bit rate detection period spaced by a bit rate detection interval when an error occurs in bit synchronism;   producing a bit rate detection signal upon coincidence of said detected bit rate with said signal bit rate; and   switching said receiver section into a temporary continuously activated state to establish said frame synchronism before lapse of a frame synchronism establishing interval, wherein said switching step comprises the steps of:   determining a unit time interval shorter than each of said frame periods; and   using said unit time interval repeatedly as said bit rate detection interval.   
     
     
       22. A battery saving method as claimed in claim 21, wherein said using step repeatedly checks for production of said bit rate detection signal once within said unit time interval during said frame synchronism establishing interval. 
     
     
       23. A battery saving method as claimed in claim 21, said radio signal comprises frame periods of a predetermined number of codewords of a common codeword length, wherein said determining step determines said unit time interval is not longer than a fraction of a total codeword length of the codewords in each of said frame periods. 
     
     
       24. A battery saving method as claimed in claim 23, wherein said predetermined number is equal to an integral multiple of four, and wherein said determining step determines said unit time interval corresponds to four times said common codeword length. 
     
     
       25. A selectively called radio receiver, operable in a battery saving mode, for receiving a radio signal having a bit rate and comprising successive frame periods, said radio receiver comprising: a receiver section for receiving said radio signal as a reception signal to establish bit synchronism between said receiver section and said reception signal, and wherein said receiver section establishes frame synchronism with frame periods of said reception signal following establishment of said bit synchronism;   bit rate detecting means for detecting a bit rate of said reception signal for a bit rate detection period spaced by a bit rate detection interval when an error occurs in bit synchronism to produce a bit rate detection signal upon coincidence of said detected bit rate with said signal bit rate; and   control means for switching said receiver section to establish said frame synchronism before lapse of a frame synchronism establishing interval, wherein said control means comprises:   determining means for determining a unit time interval shorter than each of said frame periods; and   using means for using said unit time interval repeatedly as said bit rate detection interval.   
     
     
       26. A selectively called radio receiver as claimed in claim 25, wherein said using means repeatedly checks for production of said bit rate detection signal once within said unit time interval during said frame synchronism establishing interval. 
     
     
       27. A selectively called radio receiver as claimed in claim 25, said radio signal comprises frame periods of a predetermined number of codewords of a common codeword length, wherein said determining means determines said unit time interval is not longer than a fraction of a total codeword length of the codewords in each of said frame periods. 
     
     
       28. A selectively called radio receiver as claimed in claim 27, wherein said predetermined number is equal to an integral multiple of four, and wherein said determining means determines said unit time interval corresponds to four times said common codeword length.